This invention relates to a jet weaving machine which includes an inserting nozzle at one end of the shed, a guide channel comprised of lamellae (e.g., the reed dents) arranged over the width of the warp shed, for guiding the weft thread during insertion in the shed, a first weft thread monitor disposed in the region of the far end of the shed for emitting a signal when the inserted weft thread has not reached its intended length, and a tensioning device located beyond the first weft thread monitor in the direction of the weft insertion, for stretching and holding the inserted weft thread until beating-up is performed, said tensioning device being in the form of an element through which an auxiliary fluid flows to take the head of the inserted weft thread which projects out of the shed and bend it transversely away from the weft insertion direction.
In these and other weaving machines the weft thread is susceptible to breakage during its insertion in the shed. Instances of this are known as "bursting the weft". These may not be recognized as weft defects by the first weft thread monitor, since the arrival of the broken forward part of the weft thread at the first weft thread monitor is interpreted by the monitor as correct weft insertion.
In West German Offenlegungsschrift No. 25 17 471, in connection with a gripper weaving machine a weft thread monitoring device is described with which "bursting of the weft" or so-called "overshoot" can also be recognized. This device has a second weft thread monitor at a distance from the first weft thread monitor and aligned with it. The second weft thread monitor emits a signal if the inserted weft thread overshoots its intended length by a prescribed distance.
It would be desirable to be able to equip a jet weaving machine of the type described initially above with a second weft thread monitor. However, thus far this has not been considered feasible, because, in the first place, the leading end of the inserted weft thread is always engaged in i.e., passes all the way to the tensioning device, hence the second weft thread monitor may not be disposed ahead of the tensioning device; and in the second place, the leading end of the weft thread does not fly through the tensioning device in the shooting direction, regardless of whether there is "bursting of the weft", hence for this reason the second weft thread monitor cannot be disposed in alignment with the first weft thread monitor, but may be disposed, apparently, beyond the tensioning device.
The underlying object of the present invention is to devise a jet weaving machine of the type described initially above, wherein either "overshoot" or "bursting of the weft" will be recognized as a weft defect.
This object is achieved according to the invention by a second weft thread monitor disposed in the region of the exit end of the auxiliary fluid flow from the tensioning device, whereby said second monitor emits a signal if the inserted weft thread overshoots its intended length by a prescribed amount.